The present application generally relates to exoskeletons, and, more particularly, to an exoskeleton control design framework that shapes the frequency response magnitude profile of an integral admittance of a coupled human-exoskeleton joint so that a desired assistance is achieved, while ensuring coupled stability and passivity.
Exoskeletons are electromechanical devices that may physically and energetically interact with and provide assistance in the motion of human joints and/or limbs. Over the last two decades, exoskeleton devices have been developed to assist humans in their physical activities. (A. M. Dollar and H. Herr, “Lower extremity exoskeletons and active orthoses: Challenges and state-of-the-art,” IEEE Trans. Robotics, vol. 24, no. 1, pp. 144-158, 2008; D. P. Ferris, “The exoskeletons are here,” Journal of Neuroengineering and Rehabilitation, vol. 6, no. 17, pp. 1-3, 2009; and R. A. R. C. Gopura, K. Kiguchi, and D. S. V. Bandara, “A brief review on upper extremity robotic exoskeleton systems,” in Proc. IEEE Int. Conf. Industrial and Information Systems (ICIIS), 2011, pp. 346-351.). Exoskeleton devices have been used for rehabilitation (N. G. Tsagarakis and D. G. Caldwell, “Development and control of a ‘soft-actuated’ exoskeleton for use in physiotherapy and training,” Autonomous Robots, vol. 15, no. 1, pp. 21-23, 2003; A. Gupta and M. K. O'Malley, “Design of a haptic arm exoskeleton for training and rehabilitation,” IEEE/ASME Trans. Mechatronics, vol. 11, no. 3, pp. 280-289, 2006; and A. U. Pehlivan, O. Celik, and M. K. O'Malley, “Mechanical design of a distal arm exoskeleton for stroke and spinal cord injury rehabilitation,” in Proc. IEEE Int'l. Conf. Rehabilitation Robotics, 2011. Exoskeleton devices have been used for haptic interaction (T. Koyama, I. Yamano, K. Takemura, and T. Maeno, “Multi-fingered exoskeleton haptic device using passive force feedback for dextrous teleoperation,” in Proc. IEEE/RSJ Int. Conf. Intelligent Robots and Systems (IROS), 2002, pp. 2905-2910 and A. Frisoli, F. Rocchi, S. Marcheschi, A. Dettori, F. Salsedo, and M. Bergamasco, “A new force-feedback arm exoskeleton for haptic interaction in virtual environments,” in Proc. World Haptics Conf., IEEE Computer Society, 2005, pp. 195-201) as well as for performance augmentation (H. Kawamoto and Y. Sankai, “Power assist system hal-3 for gait disorder person,” in Proc. Int. Conf. Comput. Helping People Special Needs (ICCHP), 2002, pp. 196-203; H. Kazerooni and R. Steger, “Berkeley lower extremity exoskeleton,” ASME J. Dyn. Syst., Meas., Control, vol. 128, pp. 14-25, 2006 and G. T. Huang, “Wearable robots,” Technol. Rev., pp. 70-73, July/August 2004).
Exoskeleton devices have been developed for assisting in walking and load carrying (H. Kazerooni and R. Steger, “Berkeley lower extremity exoskeleton, ASME J. Dyn. Syst., Meas., Control, vol. 128, pp. 14-25, 2006; J. E. Pratt, B. T. Krupp, C. J. Morse, and S. H. Collins, “The RoboKnee: An exoskeleton for enhancing strength and endurance during walking,” in Proc. IEEE Int. Conf. Robotics and Automation (ICRA), 2004, pp. 2430-2435; and C. J. Walsh, K. Endo, and H. Herr, “A quasi-passive leg exoskeleton for load-carrying augmentation,” Int. J. Humanoid Robotics, vol. 4, no. 3, pp. 487-506, 2007.); upper body motions (K. Kiguchi, K. Iwami, M. Yasuda, K. Watanabe, and T. Fukuda, “An exoskeletal robot for human shoulder joint motion assist,” IEEE/ASME Trans. Mechatronics, vol. 8, no. 1, pp. 125-135, 2003; J. C. Perry, J. Rosen, and S. Burns, “Upper-limb powered exoskeleton design,” IEEE/ASME Trans. Mechatronics, vol. 12, no. 4, pp. 408-417, 2007; and R. A. R. C. Gopura and K. Kiguchi, “SUEFUL-7: A 7-dof upper limb exoskeleton robot with muscle-model-oriented emg-based control,” in Proc. IEEE/RSJ Int. Conf. Intelligent Robots and Systems (IROS), 2009, pp. 1126-1131.) and whole body motions (H. Kawamoto and Y. Sankai, “Power assist system hal-3 for gait disorder person,” in Proc. Int. Conf Comput. Helping People Special Needs (ICCHP), 2002, pp. 196-203; G. T. Huang, “Wearable robots,” Technol. Rev., pp. 70-73, July/August 2004; and S. Marcheschi, F. Salsedo, and M. Bergamasco, “Body Extender: Whole body exoskeleton for human power augmentation,” in Proc. IEEE Int. Conf Robotics and Automation (ICRA), 2011, pp. 611-616.).
While assisting a human appears to be the objective of most exoskeleton devices, the term “assist” varies depending on the application. For example, an exoskeleton may be a prosthetic device that assists an amputee by providing a substitute to the lost limb (R. Versluys, G. Lenaerts, M. V. Damme, I. Jonkers, A. Desomer, B. Vanderborght, L. Peeraer, G. V. der Perre, and D. Lefeber, “Successful preliminary walking experiments on a transtibial amputee fitted with a powered prosthesis,” Prosthetics and Orthotics International, vol. 33, no. 4, pp. 368-377, 2009; J. K. Hitt, T. G. Sugar, M. Holgate, and R. Bellman, “An active foot-ankle prosthesis with biomechanical energy regeneration,” Journal of Medical Devices, vol. 4, no. 1, p. 011003-011011, 2010; and H. M. Herr and A. M. Grabowski, “Bionic ankle-foot prosthesis normalizes walking gait for persons with leg amputation,” Proc. Biol. Sci., The Royal Society, vol. 279, no. 1728, pp. 457-464, 2012.); or a device that assists a paraplegic to recover the motor function of the limb (K. Suzuki, G. Mita, H. Kawamoto, Y. Hasegawa, and Y. Sankai, “Intention-based walking support for paraplegia patients with robot suit hal,” Advanced Robot., vol. 21, pp. 1441-1469, 2007; A. Tsukahara, R. Kawanishi, Y. Hasegawa, and Y. Sankai, “Sit-to-stand and stand-to-sit transfer support for complete paraplegic patients with robot suit hal,” Advanced Robot., vol. 24, pp. 1615-1638, 2010; and R. Farris, H. Quintero, and M. Goldfarb, “Preliminary evaluation of a powered lower limb orthosis to aid walking in paraplegic individuals,” IEEE Trans. Neural Syst. Rehabil. Eng., vol. 19, no. 6, pp. 652-659, 2011.).
One type of exoskeleton device provides performance augmentation to non-pathological humans. Such exoskeleton devices focus on assisting physically weak humans regain their lost power and agility, as well as focusing on assisting physically strong humans achieve improved human performance. Assistance for performance augmentation devices may be defined as the reduction in metabolic cost of a human activity (D. Ferris, G. Sawicki, and M. Daley, “A physiologist's perspective on robotic exoskeletons for human locomotion,” Int. J. Humanoid Robots, vol. 4, no. 3, pp. 507-528, 2007.). Researchers have demonstrated reduction in metabolic cost for human walking with tethered exoskeleton devices, whose power supply is off-board the device (D. P. Ferris, J. M. Czerniecki, and B. Hannaford, “An ankle-foot orthosis powered by artificial pneumatic muscles,” J. Appl. Biomech., vol. 21, no. 2, pp. 189-197, 2005; G. S. Sawicki and D. P. Ferris, “Mechanics and energetics of level walking with powered ankle exoskeletons,” J. Exp. Biol., vol. 211, no. Pt. 9, pp. 1402-1413, 2008; and P. Malcolm, W. Derave, S. Galle, and D. D. Clercq, “A simple exoskele-ton that assists plantarflexion can reduce the metabolic cost of human walking,” PLoS One, vol. 8, no. 2, p. e56137, 2013). For activities like hopping, which involve spring-like behavior, researchers have demonstrated reduction in metabolic cost by adding passive elements parallel with the human joints (A. M. Grabowski and H. M. Herr, “Leg exoskeleton reduces the metabolic cost of human hopping,” J. Appl. Physiol., vol. 107, no. 3, pp. 670-678, 2009 and D. J. Farris and G. S. Sawicki, “Linking the mechanics and energetics of hopping with elastic ankle exoskeletons,” J. Appl. Physiol., vol. 113, no. 12, pp. 1862-1872, 2012.). However, this is an exception since the activity of hopping is particularly suited for such assistance.
Presently, no autonomous, self-contained exoskeleton devices have provided a reduction in metabolic cost for walking or running. Therefore, it would be desirable to provide a system and method that overcome the above. The system and method would modify the coupled human-exoskeleton system dynamics such that the desired assistance is achieved by using integral admittance shaping to shape the frequency response magnitude profile of the integral admittance of the coupled human-exoskeleton joint such that the desired assistance is achieved, while guaranteeing coupled stability and passivity.